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Exam 2 -- Fall 2007 -- Blank

Exam 2 -- Fall 2007 -- Blank - I(27 points Name Page 1...

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Name _______________________ Page 1 F.07.210E2 I. (27 points) Malayamycin A, a compound with antifungal and antibacterial activity, was isolated from a soil organism ( JOC 2007 72, 6353). O N H H H H 3 CO H N H N N O NH 2 H O H 2 N HO H 12 A. During the synthesis of Malayamycin A, the following substitution reaction was carried out in two stages. Complete the reaction as required. O O O O O H O Na H Na H + H 2 CH 3 Br B. A certain reaction ( H -> K ) proceeds through intermediate I . Here are some data about the reaction: G° from H to K = -2 kcal/mol G° from I to K = -10 kcal/mol G (activation energy) from K to I = 12 kcal/mol G ˇ (activation energy) from H to I = 16 kcal/mol 2 kcal/mol E progress of reaction Circle all of the tetrahedral stereocenters and clearly assign the stereochemical configuration ( R or S ). (a) (b) (a) Draw an Energy diagram that is consistent with these data. Label I and K , and show the appropriate energy curves. (b) What is the rate determining step for the reverse reaction? H Reaction Coordinate (Energy) Diagram + NaBr 2 2 8 3
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Name _______________________ Page 2 F.07.210E2 II. ( 20 points) The following electrophilic addition reaction results in a mixture of regioisomers ( P and Q ). CH 3 Cl CH 3 OH catalytic H 2 SO 4 Cl CH 3 O Cl CH 3 O P Q (a) Answer or complete the following: (i) Which of these ( P or Q ) is the major regioisomer? circle one: P Q Provide the structure for the single most important intermediate that is used to explain the regioselectivity, that is, why the major isomer is favored. Show the most significant resonance contributor.
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